Discharges from diverse industrial facilities, inclusive of accidental spills and the runoff from dumpsites, have created direct hazards to the use of land. Serious drinking water contamination and other health problems have sometimes resulted. Marshlands and estuaries have likewise been adversely affected by the runoff from contaminated streams.
Effluents containing dispersed metals components, or solutions of a metal compound, or metal compounds, e.g. salts, represent a major class of metal contamination. Metal compounds, or salts produced as by-products of diverse industrial facilities often require cleanup for removal of metals prior to discharge to the environment. Likewise, a need or desire may exist to economically recover the metals values. For example, the salts of gold, platinum and silver, e.g., silver salts, such as silver chloride, a metal salt of considerable value, is often found in the waste streams of certain industrial processes, for which reason per se its recovery is highly desirable. Other contaminant metals, e.g. such heavy metals as lead, mercury, chromium, and zinc are toxic and hazardous per se. Hence these metals may present a health risk if not removed from the by-product streams of industrial plants prior to discharge to the environment. Yet other contaminant metals may constitute both a health hazard and an economic loss due to the potential value of the metals, e.g. zinc, chromium, cadmium and nickel. Sometimes too, it is necessary to remove non-toxic metals, e.g. iron, calcium and magnesium, from process streams because their presence is detrimental to downstream unit operations.
A large number of materials of considerable diversity have been reported, in the technical and patent literature, as capable of removing a variety of environmentally unacceptable compounds, inclusive of metals, from solution, albeit these materials may in many cases leave much to be desired in terms of their specificity and effectiveness. Some of these materials are characterized as chars, ashes, and slags.
In U.S. Pat. No. 4,170,550, there is described a process for reducing the quantity of foul aqueous effluents in a raw off-gas containing environmentally unacceptable compounds such as sulfur, hydrogen cyanide, ammonia and compounds of sulfur, hydrogen cyanide and ammonia, and dissolved salts of heavy metals. The raw gas from a gasifier containing such impurities is recycled to the gasifier wherein these components are oxidized, reduced, or decomposed into environmentally innocuous compounds that can be released to the atmosphere, or removed with the residue.
In U.S. Pat. No. 4,377,483 a steel slag is employed as a contact material for the removal from a liquid of at least one dissolved metal, such as mercury, cadmium, lead or chromium. The metal, or combination of metals, is absorbed and fixed on the slag particles which are then separated from the waste liquid.
Japanese Pat. No. 53-60372 discloses the use of a steel slag to neutralize acidic metals-containing aqueous streams, the heavy metals absorbing as hydroxide onto a porous calcium silicate; Japanese Pat. No. 54-137490 discloses the removal of arsenic and heavy metals by neutralization with a steel slag or a H.sub.3 PO.sub.4 containing stream: and Japanese Pat. No. 54-80273 discloses the removal of heavy metals, e.g. iron, lead and cobalt, from an aqueous waste stream after stirring with the powdered steel slag and filtering.
Japanese Pat. No. 55-134640 discloses the use of an admixture of calcined fly ash and bentonite (clay) to remove such metals as zinc, chromium, and lead from an aqueous medium: Japanese Pat. No. 52-78687 discloses the use of an admixture of calcined fly ash and bentonite (clay) to form pellets useful as an adsorbent for metals, viz. lead, zinc, copper, mercury, cadmium and chromium; and East German Pat. No. 146,444 discloses the use of fly ash to remove mercury from a solution, the mercury being bonded adsoptively and/or chemically to the ash, and then filtered.
East German Pat. No. 220,850 discloses the use of Winkler Generator Ash for the removal of mercury from waste water via passage of the waste water through a packed column. The mercury is converted to sulfide.
Japanese Pat. No. 51-10654 discloses the use of kiln ash admixed with limestone (quicklime) to clean the water of organics and various other materials.
U.S. Pat. No. 4,530,765 discloses for the removal of inorganic impurities from a stream the use of high surface area calcined materials, to wit: clay, zeolites, coal ash, fly ash and volcanic ash. The materials are calcined and activated at temperatures of 1000+.degree.C.
There is a growing need for new products and technologies to meet pollution problems in many industries. There is a present need for high quality water feed in many industries, e.g., in the electronics industry. For example, the printed circuit industry requires water with a total of only 10 parts per billion of heavy trace metals. The nuclear industry also is faced with the problem of removing trace metals from water. EPA pollution control guidelines for drinking water require a limit of one part per million parts of water (ppm) or less on most toxic metals. Further, the EPA is considering lowering the limits on certain toxic metal ions, and this will impact on a larger number of industries than presently. Precipitation, electroplating and other conventional methods can reduce the pollution by toxic metals to only the 5-20 ppm range, but this is not necessarily enough. It is becoming increasingly important to economically prepare purer water for use by processing industries, and for the discharge of purer water to the environment. Additionally, there is a need for compositions, and process for the use of such compositions, which can be employed to shield against land contamination by toxic metal solutions leaked from land fills, tanks, and impoundments. Moreover, there is a need for the development of new compositions, and the development of processes utilizing such compositions for the removal of metals from metals-containing aqueous solutions; particularly compositions of high metals loading capabilities which are more economical and efficacious for the removal of metals without difficult filtrations, and large volume handling problems.